The invention relates to a brush seal for sealing a rotor against a stator, comprising a brush housing for fastening brushes whose free ends are directed towards the stator or rotor, which brush housing is held on the rotor or stator and has a support plate.
In known brush seals, the free ends of the brushes, which are fastened in a brush housing having a front plate and a support plate, run against a sealing surface of the rotor or stator and, by this means, seal a gap between rotor and stator. When used in stationary gas turbines or aircraft engines, it is possible by means of such brush seals to economize on axial installation space, with good sealing effect in the usual arrangement, as compared with alternative seals which can be used, such as labyrinth seals.
A brush seal is known from DE 196 18 475 A1 whose brushes are angled to reduce the radial installation length. In order to improve the increased stiffness of the short, angled brush sections, a stop located in the region of the shaft sections of the brushes is provided which acts as a bending edge when the elastic brushes are deflected as a consequence of eccentricity of the rotor. In this way, the stiffness of the brushes can be adjusted without requiring an unallowably large, radial installation space.
During operation, a local temperature increase, which increases the wear, occurs at the sealing surface of the rotor or stator because of the contact with the brushes, which generally consist of steel. In addition, the small leakage which always occurs between the brushes could be reduced.
The problem on which the present invention is based consists in providing a brush seal, of the generic type described at the beginning, in which the sealing effect and the wear behavior of the brushes is further improved.
The solution of the problem is, according to the invention, characterized in that the free ends of the brushes are provided with a slide-ring for sealing the rotor against the stator.
The advantages lie in the combination of the high level of elasticity of a brush seal, by means of which the slide-ring fastened to the free ends of the brushes can readily adapt to rotor or stator deflections which are generally radial, for example between 0.2 and 0.8 mm (when the gas turbine is being started), and the excellent sliding properties of the slide-ring, which runs against the sealing surface on the rotor stator and, by this means, seals the gap between rotor an stator ver an area. In consequence, a leak generally present in the gap region through the brushes of a brush seal is avoided. Because of the better sliding properties of the slide-ring, in comparison for example with steel brushes, less wear and a smaller increase in temperature occurs at the sealing surface on the rotor or stator. The slide-ring consists of a material which has better sliding properties than the brushes, consisting of steel, of the brush seal. In consequence, the support of the slide-ring on the low-pressure end support plate in the presence of a differential pressure is also advantageous without brush hooking or the like occurring there.
The slide-ring can consist of carbon because a carbon ring can be employed even at the high temperatures occurring in stationary gas turbines or aircraft engines and carbon has better sliding properties than steel, of which the brushes consist. As an alternative, the slide-ring can also, for example, consist of a sintered metal with sliding properties.
The slide-ring can have a single-piece configuration or be segmented. In the case of a segmented slide-ring in a rotor which is directed, in the usual manner, in the axial direction of the gas turbine, the split lines extend between the individual slide-ring sections in the radial direction and are arranged to be equidistant along the periphery of the slide-ring. A segmented slide-ring makes it possible to improve the elasticity, particularly in the case of a slide-ring brush seal in which the brushes extend rectilinearly towards the rotor or stator from their fastening on the brush seal housing, it being possible to set the rectilinear brushes at an angle of between 0xc2x0 and 45xc2x0 to the radial, depending on the application. Particularly in the case of brushes set relative to the radial, a further advantage, in the case where the slide-ring in employed, consists in that a reversal of the direction of rotation of the rotors is readily possible.
The slide-ring can be sintered onto the free ends of the brushes. This can, for example, take place by means of carbon powder or the like.
As an alternative, the slide-ring can have, on its external peripheral surface, a recess in which the free ends of the brushes are accommodated and fastened, for example by brazing.
The slide-ring can be subsequently machined on its inner or outer peripheral surface which runs against the sealing surface on the rotor or stator, by grinding or the like, in order to improve the surface quality. The slide-ring can similarly be machined by grinding or the like on its side surface supported on the support plate, in particular in the case of applied differential pressure, in order to improve the surface quality.
In order to economize on installation space, the brushes can comprise shaft sections fastened in the brush housing and brush sections angled relative to the shaft sections, the free ends of which brush sections are directed towards the rotor or stator, the support plate in such a case having a longitudinal section essentially parallel to the shaft sections of the brushes and a support section angled relative to them and essentially parallel to the angled brash sections.
In order to improve the elasticity of a brush seal with angled brush sections having the free ends of the brushes, a free bending space with a stop acting as a bending edge can be provided between the shaft sections of the brushes and the support plate. In this way, the slide-ring provided on the free ends of the brushes adapts to any deflections of the rotor or stator of between approximately 0.2 and 0.7 mm, for example when a stationary gas turbine or an aircraft engine is being started. The angled brush sections having the free ends of the brushes and the angled support section of the support plate can be angled essentially at right angles to the shaft sections of the brushes and the longitudinal section of the support plate.
In order to further improve the sealing effect, in particular for the use of the brush seal in a moist environment, such as steam, the brushes can be impregnated in a silicon, silicard or Teflon dispersion because silicon, silicard and Teflon deposits itself on the brushes, essentially closes intermediate free spaces but the brushes remain movable and elastic within certain limits. The means used have to be selected as a function of the temperatures occurring.
Further embodiments of the invention are described in the sub-claims.
The invention is explained in more detail below with reference to drawings and using embodiment examples. In the drawing: